Engineering hydrology - hydrograph analysis Problem 7.18. A uniform constant intensity storm took place over a basinwhich has a drainage area of 162 km². The intensity of the rainfall is 12 mm/hrwhereas the infiltration rate (also constant) is 4 mm/hr. The measuredhydrograph at the outlet of the basin is given in Figure 7.37.Q (m³/s)10001000030 60 90 120 150t (min)Figure 7.37 Hyetograph of the storm (Problem 7.18)a) Assuming constant base flow separate the hydrograph and find the depthof surface runoff,b) Determine the duration of excess precipitation,c) Determine UH of this basin for excess rainfall duration.

Answered: Problem 7.18. A uniform constant…

Structural Analysis

6th Edition

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Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

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b) A 4-hour rain of an amount of 1 cm (i.e intensity of 1/4 cm/hr) falls over a catchment shown in Figure 1.1. The time of concentration from the lines AA, BB, CC and DD are 1, 2, 3 and 4 hours, respectively, to the site 0 where the discharge measurements are made. i. ji. iii. Isochrones Catchment area IV (1) M4 50 ha 40 ha 30 ha 20 ha Basin boundary Discharge Figure 1.1 Determine the flow hydrograph at site 0 using the time-area curve method for this 4-hr rain with an intensity distribution given by: Time (hr) 1 2 3 Rainfall intensity 1/4 1/4 1/4 (cm/hr) Verify that the resulting flow hydrograph represents a unit hydrograph of 4-hr rain in the catchment Use this unit hydrograph to obtain flow hydrograph in the catchment for the following net rainfall profile Time (hr) Net rainfall (cm) 0-4 4-8 2 4 4 1/4
Question1: (a) Given a rainfall duration of 1-hour and an effective precipitation of 1.5 cm and the hydrograph in the table below, determine the 1-hour unit hydrograph. Time (hrs) 0 1 2 3 4 5 6 7 8 9 10 Flow (m³/s) 100 100 220 512 585 460 330 210 150 105 100 (b) Use the Unit Hydrograph from the part (a) to determine the hydrograph resulting from the following rain event. Time (hrs) Excess Rainfall (cm) 0.3 1.4 0.9 1 2 3
The average rainfall values over a catchment in three successive 2-hour intervals are 3, 5 and 2 cm, respectively. The index for the catchment is taken as 0.2 cm/hour. The 2 hour unit hydrograph ordinates are given in table below. Time in hrs. Discharge m 0 2 4 m³/sec 0 10 40 6 14 16 70 50 20 10 6 0 Base flow can be taken as 7 m³/sec at the beginning of the storm linearly increasing to 9 m³/sec at 10 Hrs. after the beginning and then linearly decreasing to 8 m³/sec at 4 Hrs. after the end of direct run off. Compute the resultant flood hydrograph. 8 10 12
3. For a 2 hour, 8 mm/h intensity rainfall, the hydrograph given in Table is observed. The area of watershed is 500 km² Table: Propeller readings Time 0 flow rate (m³/s) 8 2 4 6 14 18 30 8 10 12 45 38 28 14 16 18 20 22 24. 18. 14 10 a) Obtain 2 hour unit - hydrograph for the considered flow section b) Obtain 4 hour unit- hydrograph for considered flow section. c) Obtain the hydrograph of a rainfall with 4 hour duration and 10 mm/h intensity. 24 8 8
Q3) Given the equation of infiltration curve for ascertain area given as following: I=1.3+4.2 *exp(-0.0063*t) and t in minute, compute the volume of runoff and Index of rainfall data shown below: Time (hour) 1 3 4 5 Rainfall (mm)6 8.5 12.8 12.2 6.5 3
If the concentration-time is 1hr. Thr rainfall intensity for 5 years is approximately 100 mm/hr. 1000 R=0.989 2 years 15 years R 0.9972 R =0.9976 A 20 years R-0.9984 100 R2=0.9993 10 1 10 100 1000 Duration (minutes) O True False The base flow is the synonym for the overland flow. * False O True Rainfall Intensiry (mm/hr)
A drainage basin has a area of 7322 km2. The average annual precipitation for this area is 909 mm. The average surface water flow at the outlet of the catchment is 21.4 x 108 m3/year and the average groundwater flow out of the basin is 94.6 mm/year. Assume trailing zeros are significant if present. Determine the annual average evaporation in mm/year. (give your answer to one decimal place)
QUESTION For a 2 hour, 10 mm/h intensity rainfall, the hydrograph given in Table is observed. The area of watershed is 400 km². Table; Propeller Readings Time 0 2 4 6 8 Flow Rate (m³/s) 16 22 26 10 12 14 16 18 20 38 53 46 36 32 36 22 22 24 18 16 16 a) Obtain 2 hour unit - hydrograph for the considered flow section. b) Obtain 6 hour unit - hydrograph for the considered flow section. c) Obtain the hydrograph of the rainfall with 6 hour duration and 12 mm/h intensity.
a. The streamflow from a 500-hectare catchment due to a storm of constant intensity of 27mm/h for four hours can be represented by a triangle in which the peak flow was 25 m3/s. The flow lasted six (6) hours and peaked at two (2) hours. The soil texture is uniform throughout the catchment and when the surface is ponded, its infiltration rate varies according to the Horton equation, with a decay constant, k, of 0.5 h and a maximum infiltration rate, fo, of 24 mm/h. Use the information to determine; the volume of infiltration (mm); the infiltration rate at soil saturation (mm/h); and i. ii. iii. the runoff coefficient of the catchment. iv. State your assumptions.
3. The figure below shows 5 different isohyets in a watershed. Find the average rainfall using the isohyetal method Given: The left-most side area (Zone A) can be assumed to receive a rainfall of 1 cm. The area between the isohyets are given in the following table: A Zone A B C D E F B 1 cm D E 1.5 cm 4 cm Area (km²) 80 75 95 82 68 5 2.5 cm 3.5 cm
QUESTION For a 2-hour, 10 mm/h intensity rainfall, the hydrograph given in Table is observed. The area of watershed is 400 km². Table; Propeller Readings Time 0 2 4 6 8 10 12 Flow Rate (m³/s) 16 22 26 38 53 46 36 14 16 18 32 36 22 a) Obtain 2-hour unit - hydrograph for the considered flow section. 20 22 24 18 16 16
QUESTION 3 10 A storm with 10 cm precipitation produced a direct surface runoff of 5.8 cm in the equivalent depth unit. The time distribution of the storm is given in Table below. Estimate the @-index of the storm and the excess rainfall hyetograph. Time from start (hr) Incremental 0.4 rainfall in each hr (cm) 4 6. 0.9 1.5. 3.3 T.7 1.6 1.0 0.5

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